.aif Audio Interchange Format File (AIFF)
.au Sun/Next Audio File
.mid MIDI Sequence File
.mp3 MP3 Format Sound File
.snd Sun/Next Audio File
.wav Microsoft Windows Wave Sound File
The answer to your second question is ....... you can't.
You'll see all kinds of tips and tricks telling you that you can hide your HTML from the right-click "view source" command in the browser, but take it from me, not one of them will work against someone who really wants your code. The more you try to hide your code the more attractive it will seem to someone who wants to get at it, and if you take my advice you'll forget about trying to hide it.